Coatings and other surface materials are often difficult to remove from conduits and other substrates, and there has been ample activity in the art directed to such problems, viz. U.S. Pat. Nos. 2,181,306; 2,631,315; 3,343,986; 3,495,288; and 3,820,184. In the case of thin film plastic coatings on conduits, particular epoxy coatings, removal is next to impossible due to the high adherence between the epoxy and conduit and the glass-smooth outer surface which prevents penetration by many removal methods. Such conduits are frequency damaged by vigorous removal techniques necessary to remove such materials. In the case of underwater conduits, problems are multiplied many times over. In the underwater environment, machines of the prior art generally are not adaptable for use. Removal of underwater coatings by divers is slow and expensive and the work is difficult both because of the underwater medium and the adhesive qualities of the coating. Bringing the conduit to the surface for removal of the coating is difficult, slow and expensive and abandonment of the conduit is costly and possibly hazardous. Nonetheless, the necessity for re-coating a conduit because of leakage, corrosion, etc. and for removal of the old coating to insure binding of the new coating or provide a reliable sealing surface frequently justifies such high expense. The present invention is directed to providing a new, less expensive, and more efficient technique, for accomplishing these desired results.